The present invention relates to a recording apparatus using an ink-jet type printing head.
Various conventional ink-jet type printing heads are known. However, in any type of the printing head, a single nozzle is combined with a single ink injection means. Therefore, if a nozzle clogs, ink cannot be injected toward a recording paper sheet, and desired patterns such as characters, numerals, or other symbols cannot be perfectly printed on the recording paper sheet. In particular, when a heating means is used as the ink injection means, ink is injected from an injection port of the nozzle by means of bubbles formed in the ink in the nozzle upon heating of the heating means. However, if the ink cannot be supplied to the heating means due to clogging of the nozzle, the heating means is idly operated, and may be damaged. When the heating means is damaged, since the heating means is arranged integrally with the nozzle, the printing head as a whole must be replaced.
When a combination of one nozzle and one ink injection means is applied to the manufacture of a line printer head which requires a large number of nozzles arranged at high density, a large number of ink injection means must also be arranged at high density in correspondence to the large number of nozzles. However, an alignment operation for realizing such an arrangement is very difficult to attain. Therefore, an ink-jet type line printer head in which the nozzles and the ink injection means have one-to-one correspondence has not yet been placed on the market.
Japanese Patent Disclosure (Kokai) No. 60-71260 discloses a recording apparatus having an ink-jet type printing head which can be used as a line printer head.
The recording apparatus having the ink-jet type printing head described in the above disclosure comprises ink tank 12 for storing a large quantity of ink, rotating roller 14 which is rotated inside ink tank 12, and heating means support member 16 arranged above ink tank 12, as shown in FIG. 45. A large number of heating means 18 are arranged on the upper surface of heating means support member 16 along a line perpendicular to the sheet surface. Endless film member 20 is looped between rotating roller 14 and heating means support member 16, and a large number of nozzle areas 24 each consisting of a large number of nozzle holes 22, arranged along a line perpendicular to the sheet surface, are formed on endless film member 20 at equal intervals along the longitudinal direction thereof.
Ink is filled in nozzle holes 22 of film member 20 which is driven by roller 14 when member 20 passes through ink tank 12. The ink filled in nozzle holes 22 is injected therefrom by the pressure of bubbles formed upon heating of heating means 18 when nozzle area 24 to which these holes belong is located above heating means 18 of heating means support member 16. The injected ink droplets become attached to recording paper sheet 26 which is fed near the upper surface of heating means support member 16. When corresponding heating means 18 in nozzle areas 24 are heated while recording paper sheet 26 is moved in a given direction, a desired pattern can be printed on recording paper sheet 26.
In the conventional recording apparatus having the above arrangement, ink also becomes attached to the surface of film member 20 because it is difficult to accurately maintain a predetermined distance (preferable, 0.2 mm) between film member 20 on support member 16 and recording paper sheet 26. Therefore, paper sheet 26 often contacts film member 20, and is contaminated with ink attached to film member 20. In the conventional recording apparatus, nozzle areas 24 moving out from ink tank 12 are exposed to air until they reach support member 16. Therefore, the ink filled in nozzle holes 22 of nozzle areas 24 is dried and becomes attached to inside of nozzle holes 22, thereby easily clogging the nozzles.
The above problems interfere with the practical application of the above-mentioned recording apparatus.
In the recording apparatus described in Japanese Patent Disclosure No. 60-71260, since a diameter of each nozzle hole 22 is small, a sufficient printing density cannot be obtained only by ink injected from nozzle holes 22. In order to increase the printing density, a contact angle of film member 20 with respect to the upper surface of support member 16 is decreased (about 2 to 6 degrees), the spray angle of ink injected from nozzle holes 22 is increased, and clear printing cannot be performed. If a diameter of each nozzle hole 22 is increased, although the printing density is increased, a resolution is decreased, and, again, clear printing cannot be performed.
If a double printing operation is performed in order to improve the printing density and to attain clear printing, a printing speed is decreased to half, and a resolution is also degraded as compared to a single printing operation. In addition, the service life of heating means 18 is also decreased to half.